You know a musical is a real disaster when it has what I call a "nervous breakdown," a moment (usually somewhere in Act Two) when the whole thing simply falls to pieces. Thou Shalt Not has the distinction of offering three such moments, making it Broadway's worst musical in years. While it may not eclipse Carrie, it is the first truly spectacular musical fiasco of the new millennium.

There is no disgrace in being part of such a humongous flop. It has happened to all the Broadway greats, from Ziegfeld to Tune. Thou Shalt Not is Susan Stroman's chance to join that stellar – if somewhat embarrassed – circle of legendary talents. Only someone who is incredibly gifted can create something so incredibly bad.

Stroman has no one to blame but herself. It was her idea to turn Emile Zola's early novel Therese Raquin into a musical. Tragic tales of passion and betrayal that litter the stage with corpses are more the stuff of grand opera. (Incidentally, an operatic version of the story premieres next month in Dallas.) Moving the action to atmospheric 1940's New Orleans certainly helps, but the story is so relentlessly gloomy that there is little reason for anyone to burst into song.

In brief, a jazz pianist falls in love with his buddy's nubile wife. The pianist murders his buddy, sending the buddy's mourning mother into a crippling stroke. (Does this sound like a musical to you yet?) After waiting a year, he marries his buddy's widow, but every time he tries to touch her, his buddy's ghost appears and drives them apart. In time, the wife is driven into madness and suicide, and the pianist blows his own brains out as the final curtain falls.

David Thompson's book cannot begin to make these characters sympathetic – a problem that plagued his only other Broadway musical, Steel Pier. Harry Connick Jr.'s first Broadway score is a respectable effort. He musters some fine "Big Easy" spirit for "Take Her to the Mardis Gras," but most of the songs are dramatically and melodically blah. When a seasoned musical actress like Debra Monk cannot make your material register, the material is the problem.

Susan Stroman is a superb choreographer, but not much of a book director – at least, not yet. It is clear from the earliest scenes that she has no clue which way to take Thou Shalt Not. And saddest of all, not one of her dances makes any real impact here. Whenever the story breaks down – and it often does – she sends the ensemble dancing in a circle around the stage. the effect is chaotic. Time and again, she puts staging ahead of performance. That sort of thing may get by in an all-dance show like Contact, but is death for a troubled book musical.

My heart went out to the cast members caught in this confusion. Craig Bierko and Kate Levering have tons of sex appeal, making their bedroom ballet the main visual distraction of the evening. (Hell, seeing the humpy Bierko in his skivvies was almost worth the price of admission in itself!) But these charming performers couldn't do much playing murderous lovers that everyone wants to hate, and none of their songs gives them anything powerful to work with. Norbert Leo Butz gives his all as the cuckolded husband who comes back as a barefoot dancing ghost, but the character is so annoying that one of his later appearances drew an "Oh no, not him again!" from a man in the audience. While I sympathized with Butz, I couldn't blame the heckler for his honesty.

Debra Monk gets to show some of her stuff when, silenced by a stroke, she wreaks havoc with a Scrabble game. Otherwise, her substantial talents are wasted.

The great director Moss Hart once said that the secret to failure was saying "yes" when one really meant to say "no." My advise to you is simple. When it comes to Thou Shalt Not, thou should not.